Syntax Magazine

SYNTAX ZX80

A PUBLICATION OF THE HARVARD GROUP

VOL.3 NO.3

IN THIS ISSUE

8K Programs

Theome. Tax. 6.08 os bees 8
Flashing Prompts, «..... Lg
Video Artist......... 10

Beginners’ Column
Translating Programs. .3
Book Review
Machine Language Pro-
gramming Made Simple. 20

Classified AdS....«%.<%4 rai
Curing 16K Dumping..... 20
Dear Bat COr so xsain cede Zt 14
Hardware

Ze. PETREING, .tse sn eas 4 4

Kit Misunderstanding.1l
Hardware Hints...s4vs.s. 7
Hardware Review

Marex ROM Switch..... 16
Machine Language

Flags Register....... 17
News/New products..... 2
Numbers Held Inaccurately

On the: ZKB Ee sds 1 wae 4 6
Program corrections and

improvements..... Z

Software Review
Computacalc and

Video-Plan........... 18
Software Hint........... 5
USETS” “GROUDS <i sea decas 15

Index of Advertisers

Bani T6Ch sexs ie Saeed 17
Kopak Creations........ 19
LIN Enterprises... i024 11
Minidware: GGucs 5. a2 dick 6,16
BERD SY St CMSs: we ae ae ee 20
OCS Nats od arcs oa aes 18
Sinclair Research...12,13
DORUS VN Ge asa 5 era'3: was tt oat s)
SyCAK cA eee Santee ne eA.
Zeta SOLtware.« i icuksass 7

ISSN 0273-2696 MAR., 1982

IAN LOGAN WINS FIRST ANNUAL ROSETTA STONE

Dr. Ian Logan of Skellingthorpe, UK, a
frequent SYNTAX contributor, won the first
annual Rosetta Stone award sponsored by
Mindware Co. of Wayland, MA. Given for the
best independent product--application, soft-
ware package or peripheral--for ZX80/1s,
future prizes will be awarded by SYNTAX
editors. Dr. Logan won $100, a US computer
magazine subscription, and a Rosetta Stone
replica for his 8K ROM disassembly.

To nominate a product for next year's
award, send the developer's name, address,
and phone number with a description. To
enter a product, also send the item plus
documentation to SYNTAX Rosetta Stone Award,
RD 2 Box 457, Harvard, MA, 01451.

TIMEX TO MARKET SR PRODUCTS IN NORTH AMERICA

Sinclair just announced a license with
Timex to manufacture and retail Sinclair
computers, peripherals and software via Timex
outlets in N. America. Expect the change
this fall. Sinclair will then stop selling
by mail and you can buy Sinclair products at
stores. We don't know which stores yet.

64K RAM AVAILABLE MID-MARCH

Memotech's new 64K plug-in RAM will be
available in March for $199 US. Contact
distributor Gladstone Electronics, 901
Fuhrmann Blvd, Buffalo, NY 14203, or 1736
Avenue Rd, Toronto, Ontario M5M 3Y7.

AUTHORIZED SINCLAIR REPAIR SERVICES

MicroSync Services will take over
Sinclair's repair work for ZX80s and ZX8ls
(kits and assembled) and 16K RAMs. They also
offer $10 yearly maintenance contracts. Send
SASE to MicroSynec Services, Customer Service
Dept, 162R Marlboro St, Keene, NH, 03431.

SYNTAX ERROR: Lawrence Souder
reported an error in his 4K Phone
Number Word Generator program
(Feb. 82). Line 110 should read
NEXT Z, not NEXT X.
Lori Olson's simultaneous equa-
tion program contained two typos:
80 FOR H=1 TO I-1
110 NEXT J

PROGRAM IMPROVEMENTS
Tom Finley sent these improvements

to R.F. Fraser-Smith's 8K Digital
Clock (Nov. 81):

200 IF H<10 THEN LET D=19
201 IF H>=10 THEN LET D=18
202 IF M<10 THEN LET E=22
203 IF M>=10 THEN LET E=21
206 PRINT AT 21,D;H;":00"
208 PRINT AT 21,E;M;" "smM$

To run Hexadecimal Math (Dec. 81)
with an 8K ROM, make these changes
from Leo Morgan of Peabody, MA:

90 DIM (2)

180 “LET N (1) =D

230 LET N(2)=p

240 IF C=2 THEN LET D=N(1)+N(2)
250 IF C=3 THEN LET D=N(1)-N(2)
260 IF C=4 THEN LET D=N(1) *N(2)
270 IF C=5 THEN LET D=N(1)/N(2)
370 FOR X=1 TO 4

500 DIM H(4)

580 PRINT CHR$ (H(4));CHR$ (H(3
));CHR$ (H(2));CHR$ (H(1));

Clifford Efaw of Morton, WA, sent
these changes to run 4K Blackjack
(Jan.82) with 8K ROM:

370 LET X=INT (X*52)+1

670 PRINT P(Z),CHR$ (15)

DEFENSIVE AWARI

I finally figured out the
computer's defensive moves for my
Awari program (Feb.82) to improve
the play for better players. These
additions foresee the consequences
of a second move by the human,
improving the original version in
Basic Computer Games. The addi-
tions yield approximations only--
they don't add a point to the

opponent's score for passing home
on the way to a zero pile or fora
second move--but in general they'll
make the right move. The change in
line 330 avoids repeating a previ-
ous move. You can eliminate lines
270-290 since the Sinclair won't
invariably move pile 1 following
pile 4 and leave you to move pile 5
for 6 points. Unfortunately the
initial move is always pile 4,
which is a bit repetitious.

Change these lines:

330 LET H1=-99

371 LET Q=0

372 FOR T=1 TO 6

373 IF A(T)=0 THEN GOTO 381
374 LET R=0

375 LET U=A(T)+T

376 IF U>14 THEN LET U=U-14
377 IF U=7 THEN LET A(T)=0

378 IF U=7 THEN GOTO 372

379 IF A(U)=0 THEN LET R=A(14-U
)+1

380 IF R>Q THEN LET Q=R

381 NEXT T

382 LET H2=A(14)-A(7)-Q

390 IF M=14 AND K=2 THEN LET H2
=H2+2+0

400 IF ABS (H1-H2)<1 THEN LET H2
=H2+RND-.5

Jon Passler, Beverly, MA
EDUCATIONAL SOFTWARE VENDOR

Edson Electronics now offers
educational programs for ZX80/81l1s
with elementary school level arith-
metic, spelling, and counting
exercises (9 learning plus 3 game
programs). Programs require 8K
ROM/2K RAM. Listings plus documen-
tation are $14.95, tapes are $12.95
(both for $24.95). Edson also has
a digital VU meter for $28.95 to
monitor cassette loading and help
eliminate loading problems. Edson
Electronics, PO Box 151211, Tampa,
FL 33684, 813/870-0282.

Remember to return your white
renewal card within two weeks of
our postmark to get a free SYNTAX

| magazine binder.

——

TRANSLATING PROGRAMS: ON...GO TO

Revising some programs for use
on your ZX80/81 requires total
knowledge of that computer language
and its usage. One such term that
you will stumble over is the
ON...GO TO or ON...GO SUB state-
ment. A program line might read:

90 ON X GO TO 100,10,333,2000,59

The computer compares the
value of X with the line. If X=1
then it will GO TO line 100, if X=2
then line 10, if X=3 then line 333,
etc. The same thing will happen if
the line reads:

90 ON X GO SUB 100,10,333,2000,59
Notice that if X does not
equal any number 1-5, the computer
moves to line 91. In other words,

if X equals a negative number,
zero, or a number greater than 5,
the computer skips that line.

One revision method is to list
the numbers:

90 IF X=1 THEN GOTO 100
91 IF X=2 THEN GOTO 10
92 IF X=3 THEN GOTO 333

If you use GO SUB instead of
GOTO, check for RETURN statements.
For instance, if line 92 reads IF
X=3 THEN GO SUB 333, then a line
following line 333 must have a
RETURN statement.

A second revision method is
the COMPUTED way, like 90 GO TO
X*100. If X=3, the computer goes
to line 300. Using this method,
the computer will go to any value
of X (it will even search for a
negative line number).

A third revision method is the
DIM-ARRAY way, using a dimensioned
array containing the line numbers.
See SYNTAX (Dec.81 p.18) for this
type of data storage.

The computed method uses the
fewest bytes and runs at the slow-
est speed, since it must compute
each GO TO. The listed way is
somewhat faster. The array method
is quick if the DIM statement is
near the beginning of the program.
Mort Butler,

BW Sabre, Houston, TX

iy
pr; i oo 5 Srey
ZXCHESS is the fastest, most

li, versatile chess program

available for the Sinclair. With
seven levels of play, ZXCHESS
has the ability to accept and play
all standard chess moves in-
cluding castling and en passant
captures.

This sophisticated program has a detailed =
display of the playing board and allows you to ——=_-———" \
change sides and even levels of difficulty during
agame.

You can set up the board at any point in the
game to examine a special position. If you get
stymied, the program will even suggest a move
for you.

mm i6K

SUPER INVASION REVERSI ROAD TO RICHES
CYBORG WARS WALLBUSTERS SPACE TREK

MACHINE LANGUAGE UNDERSTANDING YOUR
PROGRAMMING... ZX81 ROM

TEN EXCITING PROGRAMS _ DIRECTORY/RECORD
FOR THE 2X81: 1K

ch i he i El Be i ese ee
WRITE FOR FREE CATALOG

C1 Please sendme copiesof ZXCHESS
@ $24.95 each.

Please send me

copies of

(i Please send me a free software catalog
lenclose

Please add $1.50 shipping & handling
New York residents add sales tax.

SEND CHECK OR MONEY ORDER TO:

SOFTSYNG INC.

PO. Box 480, Murray Hill Station, New York, NY. 10156 (212) 685-2080

| Foreign orders must be paid by International Money Order or
foreign draft in U.S. Dollars drawn on a New York bank.

NAME

ADDRESS

CITY

STATE/ZIP

TECHNICAL DETAILS FOR ZX PRINTING

Although Sinclair's printer is
not available in the US yet, we got
a British model and dissected it.
We suggest that when and if you get
one, you NOT dissect it--it's
surprisingly tough to reassemble.
Here's how the ZX printer talks to
the 8K ZX80/81. (The 4K ROM does
NOT support printing.) With this
info you can start interfacing dot
print mechanisms to ZX8ls.

Your computer contains a 33-
byte buffer in RAM, named PR-BUFF,
starting at address 16444. In the
ROM, routines for LPRINT, LLIST and
COPY take character codes from this
buffer, transform them to dot
patterns using patterns stored in
ROM beginning at 1EOOH, and send
them to the bus for the printer to
use. The ZX printer accepts this
SERIAL data and prints DOTS to form
characters.

Data to the printer consists
of instructions to draw a picture
of the characters, one 32-character
(or 256-dot) line at a time. Eight
consecutive lines of dots form one
row of characters.

Although the computer and the
printer exchange several pieces of
data, the principal data are the
request from the printer to send
the next dot and the instruction
from the computer to print the next
dot. Auxiliary signals tell the
printer how to control the motor
and inform the computer that the
printer is connected and the stylus
is on the paper. All signals pass
in and out through the Z80 accumu-
lator, or A register.

ZX printers function like a TV
picture, scanning from left to
right. A belt pulls a conductive
stylus quickly across the paper,
and where a black dot is wanted a
pulse of current is passed through
the stylus. This evaporates the
aluminum coating on the paper,
exposing the black backing. To
avoid the need to return the stylus
rapidly to the left hand edge of

the paper, two styli, equally
spaced on a moving belt, follow
each other. Thus one leaves the
paper as the other arrives in quick
succession. The belt and the paper
feed roller are both driven contin-
uously while printing, so when the
next stylus comes round the paper
has moved up to the next line.

So that the styli always stop
off the paper, the BASIC commands
slow the motor for the last two
scans before stopping--this makes
the graphics join up if done in
several goes; put this feature in
any machine language program that
requires the printer to stop while
the computer works out the next
line. At full speed, each pen is
on the paper for about 32mS and off
it for about 16mS. Since the motor
speed can vary, an encoder disc is
used to give 256 pulses across a
92mm printing width (allowing 4mm
margins). These pulses are syn-
chronized with the stylus hitting
the paper to keep the printing
vertical.

There are about 60uS between
the starts of successive pulses at
full speed.

The printer is wired as a Z80
I/O port, selected by A2 being at a
low level--no other address lines
are recognized. Sinclair always
calls this port as OOFBH (25ldec)
in software, but does not fully
decode the address in hardware. So
to send information to the printer
use the Z80 command: OUT(FB) ,A--
OPCODE D3 FB, assuming the data is
in register A. The data bits have
the following meanings:

D2 high means stop the motor,
low means start it.

Dl high means put the motor at slow
speed--D2 high overrides this

D7 high applies power to stylus.

side of the
lines remain in
last, until new
printer. At
pressing the

On the printer
interface all these
the state they were
data is sent to the
switch on, or after

feed button, Dl and D7 are set low;
D2 stays high after feed. The
other data lines aren't used.

To fetch information from the
printer, the Z80 instruction: IN A,
(FB)--OPCODE DB FB--will put data
into the accumulator. These bits
are used:

D6 will be read as low if the
printer is there, high if it
isn't, and is used solely to
check if printer is connected.

DO is the signal from the encoder
disc.

D7 is high when the stylus hits the
paper.

DO and D7 are both latched on the
printer side of the interface so
they remain high until the computer
writes something to the printer.

So even if you don't make use of
the information you read in, use an
output instruction with appropriate
data to reset the latches until the
next signal. These bits may be in
either state on switch on, and are
unaffected by the feed button. The
paper detect signal is also used
internally by the printer to make
sure the styli stop off the paper.
If power is applied to the stylus,
the paper signal will go high even
if the printer is between scans;
turn the stylus off before trying
to detect the paper edge.

All printing is done in FAST
mode. The COPY command prints a
full screen in 12 seconds.

All ROM code to control print-
ing appears to lie between 0802H
and 0918H, based on a quick look at
Ian Logan's ROM disassembly. A
call to 0871H (USR 2161) prints the
characters stored in the printer
buffer, then clears the buffer.

SYNTAX (02/08/13) describes a
port interface, including a schema-
tic for another address, that you
can easily modify. Simply use
address lines AO-A7, IORQ, and RD
or WR to.select address, port, and
direction. Use DO-D7 to carry data
to and from the accumulator. Use

74LS75s to latch the data in and
out, and use LS-series gates else-
where when they connect to the
ZX80/81 bus.

You can use Ian Logan's anno-
tated ROM disassembly to examine
the Sinclair software that executes
the LPRINT, LLIST, and COPY func-
tions. You can move the COPY-BUFF
and output routines to RAM using a
program suggested in Sinclair's
printer manual. First POKE 16389,
124 and NEW to set aside memory for
the machine language routine.

Next, use the following code to
move the ROM routine to RAM.

5 FOR I=0 TO 112

6 POKE 31744+1,PEEK (2161+1)

7 NEXT

9 POKE
Call this

q
31857,201
routine using USR 31744.

routine will now read
codes, which you must
POKE into PR-BUFF, and translate
them into dot codes using the
patterns in ROM. The buffer is NOT
cleared by this routine.

If you want to store different
patterns, POKE them into the 256
bytes starting at 32256 (the space
is already set aside) and POKE
31800,63 (to restore the ROM as dot
source POKE 31800,15).

Each successive byte stores
the 8 dots for a row of printout of
one character. The ninth byte thus
contains the first row of the
second character in the set. By
defining bit patterns here you can
define a new character set. Speci-
fy all 8 bytes for each character.

This
character

SOFTWARE HINT

My son finished off a recent
program for me thusly:
9950 SAVE ''Name of. Program"
9960 GOTO (First line of Program)
To SAVE this on tape, I just type
GOTO 9950 instead of the more time-
consuming SAVE 'Name of Program!’.

Herb Sturges, Orinda, CA

. . € powerful combination at a bargain price!

MINDWARE introduces COMPUTACALC,
a low priced software package for
the ZX81. COMPUTACALC is an
electronic worksheet with an
almost unlimited range

of applications.

CONSIDER:

Financial forecasts
Engineering calculations
Productivity analyses
Pricing

Job costing

Estimating

Production scheduling

A versatile tool for $39.95
Requires 16K RAMPAK
MINDWARE has a catalog of
software. hardware and books
for the ZX81.
Write
MINOWARE CO.

“> Bostac Orst Qeas
weds ara MA T*778

MINDWARE CO.

Products that supplement nature 4 computer

NUMBERS HELD INEXACTLY ON THE ZX81

This is the first of several
articles by Dr. Frank O'Hara on
numerical errors in the ZX81's 8K
ROM floating point.--AZ

All floating-point systems
require certain techniques of
rounding, general approximation and
slightly over- or under-stating
numbers to make the arithmetic
work. The problem is particularly
acute in the ZX81 because 1) all
numbers, even integers, are held in
floating-point form; 2) of the
almost total lack of instruction in
floating-point techniques in the
manual or the literature; and 3)
the limitation of the ROM to 8K and
the premium on every byte.

In doing arithmetic on the
ZX81, it helps to know just which
numbers are held exactly in its
BASIC and which are not. This
small program shows you exactly how
any number is held on the ZxX81:

Program 1
10 INPUT X
20 LET V=PEEK 16400 +256*PEEK
16401
30 FOR I=V+l1 TO V+5
40° PRINT PEEK. 2s". ™
50 NEXT I
60 PRINT
70 GOTO 10
INTEGER POWERS OF 2: To use this
program, RUN it and first enter 0
to satisfy yourself that 0 is held
as five zeros as the manual says.
Then try some oe, aoe powers
of 2, like 1 (or 2 Qig Ob. 20%
You'll get 129 0 0 : 0: 130 0 0 0
Oe Loe OO. Oi S and: 232 0.0 30 0.
Before explaining this, let me give
you a program to generate all
integer powers of 2 from 1 to 126.
First delete line 10 from Program 1
and replace :ine 70 with 70 RETURN.
Then add these lines to give:
Program 2
(lines 30-7C .rom Program 1)
100 LET X=1
120 FOR J=1 TO 126
130 PRINT ds (4%
140 LET X=2*xX
150 GOSUB 30
160 NEXT J
Finally, make line 20 be line 110
and delete the old line 20. To
run, press GOTO 100 then NEWLINE
(NL) or ENTER. The first 22 powers
of 2 will appear, each in the form
(129 plus n) 0 0 0 O for the nth
power. To see the other 5 screen-
fuls, continue in FAST at about 7
seconds per screenful. You should
then be convinced the manual has
got it right on this point. After
seeing the 126th power (255 0 0 0
O)y ey PRINT: 252., » You" 11 get
report 6/0 for arithmetic overflow.
The ZX81 cannot hold 2 to the 127.
To see the negative powers of
2, replace line 140 by LET X=Xx/2
and change 126 to 140 in line 120.
RUN 100 and you get the powers from
274196000 One. 2 (1000
0). From -129 to -140 the powers
should all be hcid as zero (0 000
0), but here we meet our first
quirk of the ROM. On division by

2, 9-128 becomes 9-129 and_ is

promptly rounded up to 27-128 again! NEW ZX81 1K PROGRAMS by ZETA Software
So our innocuous little program has on cassette tape with listings
Try LET X=X/4, |

got us stuck here.

then GOTO 30 (NOT RUN 30) and you ZETAPAK #1; WAR GAMES
will get 0 0 0 O O and of course Bomb Run, Sub Hunter, Barrage,
report 7/70 (RETURN with no GOSUB). Fighter Pilot*, Torpedo Alley*,
If you have the patience to run the & Dragon's Teeth*(tank battle)
program again with 128 in line 120, ZETAPAK #2:BASICALLY BASIC
you can use this same method to get RANDom POKEr, Loop de loop, IF
a zero result for 2-130. If you I May, InVariablely DisARRAYed,
want a zero result for 27129 you Return Address, & PseudoPause
have to fall back on the the ZETAPAK #33 SCIFI FANTASY
otherwise less accurate type of Planetfall*, Hyperspace Display,
expression LET X=2**-129. Wormhole*, Arcade Invaders, Star
So we have a simple way of Catcher*, & Turret Laser

generating the exact representation

of integral powers of 2 on the ZX8l
(Gece ey te eee cae TO ORDER. ..Sena payment plus $2.50

as we expect from the manual, 2 is S&H to; ZETA SOFTWARE/PO Box 3522
given by (129 plus n) 0 0 O O where Greenville, SC 29608-3522

n equals -128 to 126 inclusive.

Now compare these exact
results with the expression 2**N,
To do this, produce Program 3 from
Program 2: Make sure that line 120
contains 126 and change line 140 to
LET X=2**J. RUN 100 and note the s
19 inaccuracies at the powers 13, HARDWARE HINTS
26, 27, 31, 52-54, 61, 62, 104-108
and 121-125. Running the negative Overheating: EZUG (Educational
powers reveals similar inaccuracies | Users' Group) newsletter re-ncrts a

Or write for catalog of 50+ titles.
In Europe, send inquiries only and U$1
bill or DM2 stamp to: DELTASOFT ZP2,
Osterfeldstr.79d,D-2000 Hamburg 54,GER

at corresponding negative powers. reader's solution to over: .. ing.
Note in particular that PRINT He filed off the raised Zxui name,
2**13-8192 gives .000022888184. then put a solid, block of steel
rnaG sexere 6 in the last byte is about the size of a. pack of cigar-
3/217 , about .00002. The inaccur- ettes on top of the case. A simi-
acy arises because the ROM evalu- lar copper block copper keeps the
ates 2**13 by approximate methods transformer cool. Reprinted by
as EXP (13*LN2). Of course, permission, EZUG Newsletter, Jan/

8192.00002 may be accurate enough Feb 82, p.16, Highgate School,
for most purposes, but it may help Balsall Heath Road, Birmingham B12

you to know that it is not com- 9DS England.

pletely accurate and you can always

get it exactly if you need it by Memory Loss: One of SYNTAX's
2*2**12. The same holds for any machines displayed memory loss,
other inaccurately held powers. For | partial characters and other
example, the important number 2 strange symptoms. We tracked it to
is given exactly by 2*2**30 or by defective solder joints on the
2**32/2. So Euler's famous prime component side of the board at the
can be got quickly by 2**32/2-1. regulator IC. Under a magnifier,
Next month: Positive integral defective joints look like conical
powers of 10. pits around one or more of the 7805

pins. Touching up the solder cured
Frank O'Hara, Surbiton, Surrey, UK | all the symptoms.

INCOME TAX--8K/16K

It's that time of year again
and I hope that TAX will reduce
some of the nuisance of tax return
preparation, if not the pain in the
pocket. It is designed to aid in
year-end form preparation and also
to allow periodic monitoring of tax
liability during the year. You may
be able to reduce the amount with-
held from your salary or the amount
of your quarterly payments if self-
employed. Personally, I'd rather
have the money during the year than
have the IRS hold it for me.

Lines 100-152 provide the main
menu of functions with line 170
serving as an error trap for acci-
dental entries. You can quickly
see the program's various capabil-
ities. Tax calculation includes
all arithmetic and transferring
totals to appropriate lines.

The PAUSE subroutine at lines
6000-6030 allow you to view various
displays as long as desired before
proceeding. The form selection
subroutine is at lines 7000-7214.
Although this listing includes only
Form 1040 and Schedule A, you can
add any additional forms using the
same principles illustrated. The
particular variables allow this
flexibility. Z is the offset in
line numbers for each form with
allows all line numbers and des-
criptions to be stored in a single
sequential array but allows you to
enter the line numbers on the IRS
form. P is the number of "pages"
used to display the given form.
Each value of J is the starting
line for each display page; each
value of K is the ending line.

This allows overlap of displays as
appropriate.

Lines 1000-1120 provide the
data entry function and begin with
form selection through GOSUB 7000.
You are then prompted for line
number and amount. The amount is
added to the previous total for
this line and the new total
displayed. This allows periodic

updating during the year and
revisions during year-end form
preparation. Make negative correc-
tions by entering negative numbers.

Lines 2000-2248 perform all
arithmetic for lines that require
it. Schedule A (lines 2200-2248)
must be done first so that Form
1040 (lines 2100-2182) will have
that information. Lines 2120-2122
require you to refer to the tax
tables for the tax on the amount in
Form 1040 line 34. Lines 2124-2126
request any additional taxes. The
"bottom line'' is displayed by lines
2174-2178. In the calculation of
Schedule A, the total deduction is
displayed by 2242.

Lines 3000-3080 allow you to
view all line items on the form
selected. GOSUB 7000 illustrates
its usefulness here by allowing a
short subroutine to serve for all
present and future forms. Line
numbers, descriptions and amounts
are presented. Changing the line
number I to I$ makes for a more
attractive display.

Lines 4000-4060 record the
program and all variables, includ-
ing line descriptions and amounts.
This also makes the program self-
starting upon LOADing and elimin-
ates the danger of erasing every-
thing with a RUN instead of a GOTO.

Lines 5000-5030 erase all line
amounts to let you keep the line
descriptions intact when starting a
new tax year.

Lines 9000-9050 are for
initializing the program. The REM
statements indicate direct commands
that should be entered when the
program is being initialized. Line
descriptions are typed in by first
commanding GOTO 9020. The prompt
provides a guide to the maximum
length of the description (18
spaces) by printing 16 *s after the
line number. The direct command
LET J=1 allows later addition of
forms and line descriptions.
Setting J to the new line number
saves previous entries. The number
107 is the total lines in Form 1040

and Schedule A. If you add more
forms to the program, you must
increase 107 wherever it occurs.
After initializing TAX, enter
GOTO 100 to get to the main menu
and either begin using it or record
it for later use.
Lane Lester, Lynchburg, VA
Enter all data that cannot be
computed on Form 1040 or Schedule
A. Run CALCULATE TAX routine on
Schedule A first; totals are auto-
matically transferred to Form 1040.
For lines on Form 1040 with sub-.
lines a, b, c and d, enter each
sub-item to the main line number.
The screen shows the latest entry
and the total. You can only go
forward through the form; enter
zeros until the main menu comes up
to go back.--KO
(Mar.82 listings are printed on a
Sinclair ZX printer. Comments?)

3.6; “INCOME TAX RE
6.4; “PRESS DESIRED
‘8,6; 72. ENTER DATS
oR: 8,8) "2. CALCULATE
Ae PRINT AT 16,6; °S. REVIEW oF
150: PRINT AT 22.6; "4. RECORD DA
‘ise. [PRINT AT 22,6; "5. ERASE ALi.
eee ee 488
SQ LET KEcENKEYS
WIF Kee"R" OR REESE
1987 os VAL Keei00o _

AZ@..PRINT RT
AT

THEN 30

PRINT ‘aes, Si “LINE S
StS Lg 4 L NUMBER
‘PRINT. AT 6.26;
pau

. 8.8) “ar "
SERS a iGUNT §

+a
PRINT AT 16,8; “Tora. §"
GOSUB 68G0

oh. f

2izé4 PRINT

fay RY}
iB Fi

itil

APSO

BP DU

}
rs
3 -L (32a) -L (33
“ENTER TAX FO -

“yet Sat "ow?

wool pte (AY pot

big eat eh
orrr
aa
Ser

Oh Ow ro note nnn
ip f° fe bo fo po peo pe pd
1

KH

ra

7]

c

pat
i
=~ Ror Pos

-@; “ESNMPFER ADDITET =
ONGL TAXES

i)

=L (S35) 46 (362

TQ 45
sh (4G) +h 723

beLta?yi -L (46)
aie LET LtS4) =@

Bhatia FOR T=4? FTO
zt Ht Ba) tL td}

=

= TO 61

#252 LET LtSa) sh (62) 4L¢9}
@LSda NEXT FT

#i56 LET X=L (62) -L (S43

f
1S wo Mini
ar

Fe
Be
or
G3
ai
Ori
Pit
bar
Bool gm, EL gen, yim
| a ed oO
sf errs
ui

HiS6

HiSsS IF X<8 FHEN GOTOQ 2356
#AG@ kL pita

BAGS LET LtGei =k (63! -k yeh.
2164 GOTO 2174

2266 LET Lees) =

BLOG L€64) =

2278 LET LtGS)=<

#2: LET Lot(Gay =x#+2

2ird FOR TS TT 66

276 PRINT OY F-SB,ws x; 7 CS (T)

Ces
L {O03 -£ Tho)
(6a HEM LET Lt?
3 LUF@i ah pyal eh € 723
eee a eWeek (Bs
aR Eies Lt7aY-L ¢ 74)
Bie (P32 THEN LET Lt?y
Let LET. .f L C873 4h FSI
re EF LiF) eh TFB) eh (7S)
Le) “he fe
16. LET £ CSB’ oL TAS +h (BS)
1&5 Er Lt@P2 4h 88) +L t6a)
ae Er L(Q43 4h (821 4+ (953
e@m@e LET Lo ak (O62 +h R72
@e2d LET Lt sh. ¢FG3
2e26 LET L.¢ bal (Sa)
Sead LET L. ¢ tha skh th
Base LEP Let wd of Tiaehd
Ba3e LEY Lo € 2a) <b ts
eaeoed LET Lt bei ab goes
eG LEY LORDS? sh (ok ah P2A@) +h 03
WAP PL CLS) LCR) +h Phe
S236 LEP Lt ier) «bh (28S) -£ (186)
eae Lth@e: si ¢4@5) THEN LET L

273 =@
racee Oe eed ee Pins 25,8; “423 “;OS(1@?7}

eed GOSUB Geee
=

Bheun a7eee

FOR N=2 TO
FOR I=.itNi Fa KUM}
LET Ie=<STRe Tf

3030 PRINT t4;"% “sOetrer3;" g*sn| VIDEO ARTIST--8K/2K
CI+Z)}
3080 BOSUB Seoe This program shows the ZX81's

ability to draw pictures under
BASIC control. Run the program and
enter the title of your work. Hit

CLs
PRINT AT 6&6,

cone 73 PREPARE RECCH! NEWLINE of ENTER, and you. get. a
4a2 aNT oe 20.5; “PRESS ANY KE| flashing cursor in the center of

the screen. This is the editing
cursor. Control the direction of
this cursor in real-time with keys
5-8. The cursor moves in the
direction of the arrows on the
keys. In this mode you can move
anywhere on the screen.

PRINT. (AF 280 02 RES ERR SES To start drawing, press l.
ERASED a - A
999 REM Sees | " This puts the computer in plot
coves ease A aes 23, "PRESS ANY KE mode. Again, you have real-time
60.8 PAUSE 4ee8ce directional control by pressing
Sone SE TURN keys 5-8. To erase, go back to
Spee CL ae edit mode (hit 0) and move the
7ea8.f PRINT AT 6,7; "PRESS DESIRED Oe ose ae Syne bye
7O20: PRINT ar 6.9; "2. FORM 1648") you can save it on tape. Turn on
783: PRINT 9.9: "2. SCHEDULE Al your recorder and press $. It
rose. PAUSE. 49020 saves under the title you gave it.
Bae ae KSeTa Sa Kes"2" THEN GO You can exit just about any
rer 2b time by pressing BREAK. This
7eee sos 6suB vat Ke2100+7000 | program should run in 2K RAM for
rd those of you who have modified your
y
ae @ PRINT AT «Foret .@ «| 2X81's or added a 16K RAM pack.
7i@e° LET z2@ *
PL@4 LET Pet _ ne We i MI
a $ LET OUD 97, Lance Ward, Lansing,
PUI@ CET 3(3) =37 S LET x=232
otaa CET Rta) aed 4@ LET ¥
1 tips 2 :
7226 LET K 68) =37 415 PRINT RENTER TITLE
7izs. Ler K £3) =54 Se Gls. %
fies berate oe Scar
Zeae PRINT AT cir Aida cat atal so UNPLOT | ces THEN LET X=X-=
ri 3
vee4 LET Pee 6@ IF INKEYS="6" THEN LET Y=Y-
eee rer Jf} 23, ;
ir 2 aS == £ othe ~y
oeoe LET Ktid =20 | 7@ IF INKEYS="7" THEN LET Yay+
fede Ler ole) eet | 88 IF INKEY$="S" THEN LET X=X+
— 22 iF_ENKEY $="2" THER GOTQ 166
1@Q PLOT X,Y
anne TF INKEY $="S" THEN LET X=xX-
; 1228 IF INKEY&="6" THEN LET YevY-
TT 23@ IF INKEY$="?7" THEN LET Y=VY+
pa 1
93625 LET I =STRS Ir “ attest =k
9838 PRINT AT 21.0; TG; “eeeeeeees Ate RE RPE ee SR ME er aes
HLXERE ab aies e
348" Hcur osm 50 3 HMEVES SHEN 2802 2g
Base NEXT : 17@ GOTO 16@
SYNTACTIC SUM: S2566. 5K SYNTACTIC SUM: 23487. 68K

10

ANOTHER $100 MISUNDERSTANDING

I just finished rebuilding my
ZX81 kit. If Sinclair had sent
complete instructions with my kit
(delivered in early Jan.82) I would
not have needed to reopen the case,
desolder and remove two components,
and add seven new ones. I can't
believe that Sinclair singled me
out to receive a kit with incom-
plete instructions, so what follows
may help others whose ZX81s won't
work and wonder why they have two
resistors, two capacitors, two
little red coils and an oddly
shaped metal strip left over after
finishing the assembly per
instructions.

Instructions with my kit
called for only 12 capacitors (Cl-
C12) to be installed on the board.
They didn't mention two red-wire
induction coils. They offered no
special instructions for installing
R27 and R29. And they didn't even
mention a grounding strip, let
alone describe how to installi one.
If the instructions you got are
similarly lacking, take note.

Sinclair advises (after I
wrote) that you install R27 and R29
vertically. You should find two
pairs of resistors of the correct
values (R27=1K, R29=1M). Use the
pair that are preformed for verti-
cal installation.

You will also find two surplus
47nF capacitors (marked 473 Z) when
you finish the assembly per the
instructions. These are C13 and
C14. It's easy to spot the board
location tor. .613;, but the callout

for C14 is hidden under the 9V
jack. The C14 location is between
the end of the jack and the edge of
the board.

It is easy to spot the
locations for inductors I1 and 12,
just above the regulator. Plug the

red-wire coils into these locations
(Il and 12 bring the 9V supply to
the regulator, without them the
board is stone-cold dead). Solder
all these components to the board.

NOW AVAILABLE

CRON onc

e Standard Computer Keyboard

¢ Type programs in half the time
° Minimize errors

e Wired keyboard hooks up in minutes

Plans for keyboard conversion with reverse video
NOW $5.00

Keyboard with complete parts and plans NOW $55.00
Wired keyboard, complete with plans NOW $75.00

Add $5.00 mailing charge for continental U.S.
Other locations write for details.

Mail for information:
L.J.H. Enterprises

P.O. Box 6305, Orange, CA 92667
or call 714/547-8717

Finally, install the left-over
weird-looking metal strip so that
its long bent-up end passes between
the heat sink and the edge of the
board, with that end in position to
contact the top of the case once
the board is screwed down. Solder
the other end of the strip to the
arrow-shaped area just below the
slot in the board. Then solder the
other portion of the strip with a
single small hole in it to the
rectangular area provided adjacent
to the regulator.

My 8K/1K ZX81 ran satisfactor-
ily with horizontal rather than
vertical resistors, without the two
additional capacitors, and without
the grounding strip. It runs even
better now with the changes and
added components. The TV display
is clearer and more steady and
seemingly, keyboard entry is faster
and easier.

Bob Nadler, Englewood, NJ

Introducing
the Sinclair ZX81

If you're ever going to buy
a personal computer, now is the
time to do it.

The new Sinclair ZX81 is the
most powerful, yet easy-to-use
computer ever offered for anywhere
near.the price: only $149.95* completely
assembled.

Don’t let the price fool you. The
ZX81 has just about everything you
could ask for in a personal computer.

A breakthrough
in personal computers

The ZX81 is a major advance over
the original Sinclair ZX80—the world’s
largest selling personal computer and
the first for under $200.

In fact, the ZX81’s new 8K Extended
BASIC offers features found only on com-
puters costing two or three times as much.

Just look at what you get:

B Continuous display, including moving
graphics

B Multi-dimensional string and numerical
arrays

*Plus shipping and handling. Price includes connectors
for TV and cassette, AC adaptor, and FREE manual.

@ Mathematical and scientific functions

accurate to 8 decimal places

M Unique one-touch entry of key words

like PRINT, RUN and LIST

@ Automatic syntax error detection and

easy editing

B® Randomize function useful for both

games and serious applications

Built-in interface for ZX Printer

@ 1K of memory expandable to 16K
The ZX81 is also very convenient

to use. It hooks up to any television set

to produce a clear 32-column by 24-line

display. And you can use a regular

cassette recorder to store and recall

programs by name.

If you already own a ZX80
The 8K Extended BASIC
chip used in the ZX81 is available
as a plug-in replacement for your
ZX80 for only $39.95, plus shipping
and handling—complete with new key-
board overlay and the ZX81 manual.

So in just a few minutes, with no
special skills or tools required, you can
upgrade your ZX80 to have all the
powerful features of the ZX81. (You'll
have everything except continuous dis-
play, but you can still use the PAUSE
and SCROLL commands to get moving
graphics.)

With the 8K BASIC chip, your
ZX80 will also be equipped to use the
ZX Printer and Sinclair software.

Order at no risk**

We'll give you 10 days to try out
the ZX81. If you’re not completely satis-
fied, just return it to Sinclair Research
and we'll give you a full refund.

And if you have a problem with
your ZX81, send it to Sinclair Research
within 90 days and we'll repair or replace

it at no charge.
**Does not apply to ZX81 kits.

NEW SOFTWARE:Sinclair has
published pre-recorded pro-
grams on cassettes for your
ZX81, or ZX80 with 8K BASIC.
We're constantly coming out
with new programs, so we'll
send you our latest software
catalog with your computer.

ZX PRINTER: The Sinclair ZX
Printer will work with your ZX81,
or ZX80 with 8K BASIC. It will
be available in the near future
and will cost less than $100.

16K MEMORY MODULE:
Like any powerful, full fledged
computer, the ZX81 is expand-
able. Sinclair’s 16K memory
module plugs right onto the
back of your ZX81 (or ZX80,
with or without 8K BASIC).
Cost is $99.95, plus shipping
and handling.

ZX81 MANUAL: The 2X81
comes with a comprehensive
164-page programming guide
and operating manual de-
signed for both beginners and
experienced computer users.
A $10.95 value, it’s yours free
with the ZX81.

Introducing
the ZX81 kit

If you really want to
save money, and you enjoy
building electronic kits, you
can order the 2X81 in kit form
for the incredible price of just
$99.95* It's the same, full-featured
computer, only you put it together
yourself. We’ll send complete, easy-
to-follow instructions on how you can
assemble your ZX81 in just a few hours.
All you have to supply is the soldering iron,

How to order

Sinclair Research is the world's larg-
est manufacturer of personal computers.

The ZX81 represents the latest
technology in microelectronics, and it
picks up right where the ZX80 left off.
Thousands are selling every week.

We urge you to place your order
for the new ZX81 today. The sooner you
order, the sooner you can start enjoying
your own computer.

To order, simply call our toll free
number, and use your MasterCard or VISA.

ae To order by mail, please use the
al PRICEt QTY. AMOUNT
\.

s Zx81 | $149.95
aad ZX81 Kit
8K BASIC chip (for ZX80)

6K Memory Module (for ZX81 or ZX80) | 99.95 |
Shipping and Handling | ___4.95 | $4.95
— TOTAL

MAIL TO: Sinclair Research Ltd., One Sinclair Plaza, Nashua, NH 03061.

doupon. And send your check or money
order. We regret that we cannot accept
purchase orders or C.O.D's.

CALL 800-543-3000. Ask for op-
erator #509. In Ohio call 800-582-1364.
In Canada call 513-729-4300. Ask for
operator #509. Phones open 24 hours
a day, 7 days a week. Have your Master- / “
Card or VISA ready. é

These numbers are for orders
only. For information, you must write to
Sinclair Research Ltd., 2 Sinclair Plaza,
Nashua, NH 03061.

Smciair |

hs

han,

NAME

ADDRESS

CITY/STATE/ZIP.
t U.S. Dollars

DEAR EDITOR:

Here's a better way to stop
the listing and editing of an 8K
program. Make the first line of
your program 1 REM X. After typing
in your program, enter with no line
number POKE 16514,118 and POKE
16509,40. This will stop the list-
ing. When you try EDIT or LIST, it
gives you A241 REM no matter where
the program cursor is.

To get out of this mode,
16509,0 and POKE 16514,6l1.

POKE

Andrew Lederman, Pittsford, NY

In the Feb.82 issue, George
Luhrs asked for a linear regression
program. We have one for 8K ROM/
1K RAM or more for $2.50. It puts
the best line through x,y data
points. Ask about our business
Linear Programming system.

If you're strung for bytes,
use LET A=0 and LET A=A+l instead
of DIM A(1) and LET A(1)=A(1)+1 for
the sum-to-memory and counter
method I described in Feb. 82.

Paul Ezra, Ezra Group II, Box 5222,
San Diego, CA, 92105, 714/584-8291

In spite of Gary Vincent's
authoritarian tone in his Feb.82
letter about painting heat sinks, I
believe he is incorrect.

Copies of applicable sections
of the Motorola and National Volt-
age Regulator Handbooks are
enclosed to document the positive
effects of painting aluminum heat
sinks black. The effect of
increased emissivity varies with
the heat sink's parameters but
black paint always helps!

Chuck Hutton, Atlanta, GA
Chuck included tables from the
Handbooks showing emissivity values
for various surfaces. Painted or
varnished surfaces have higher
emissivities than polished or
oxidized surfaces.--AZ

L'd like to hear from anyone
interested in putting FORTH on the
ZX80/81 or in defining a "standard"
mapping between the ASCII and 2X81
character sets.

Rich Holmes, 1303 E. Wilson #204,

Batavia, IL, 60510

I bought an 8K ROM and 16K RAM
module for my ZX80. Here are some
problems I found and my solutions:

1. The ZX81 keyboard overlay
won't lay flat and bows up in the
center when attached. Apply double
sticky tape and press it onto the
existing keyboard. It lays flat
and keyboard sensitivity is
unchanged.

2. The 16K RAM fits loosely, as
it's only attached by the edge
connector. If it comes loose with
power on, the RAM may be damaged.
Fit a 2"x5" piece of thin PC board
material between the RAM foot. pads,
through the edge connector slot in
the ZX80 case (1 whittled mine out
a little with a pen knife) and
under the ZX80 PC board. Attach it
to the RAM and to the bottom half
of the ZX80 case with short, self-
tapping screws. Reconnect the
internal gournd spring (supplies
ground from the PC board to the
lower case coating) elsewhere.

3. The 16K RAM internal ribbon
connector leads were not clipped
during assembly at the factory.
the leads intermittently contact
the conductive coating inside the
case. As the coating has ground
applied, the consequences are
disastrous. Clip the leads.

So

Larry Lockwood, Yorba Linda,

Is anyone selling the MicroAce
Flicker-Free kit for upgraded ZX80s
and MicroAces stateside?

I got two surplus keyboards
from John J. Meshna Inc. A fantas-
tic buy for $20 each. On my 4K/16K
system I mounted the computer (out
of its case), 16K RAM and power
supply in the keyboard. I removed

the cassette ports and remounted
them at the back of the keyboard
housing. I used the keyboard's 4
red keycaps for cursor functions,
10 black keycaps for numerics, and
the remaining keys for standard
alpha functions and separate tokens
(such as TO, THEN, AND). I used
the circuitry mentioned in SYNTAX
(Vol.1 No.2) for the use of the
extra keys without holding the
SHIFT down. This keyboard was
fairly easy to wire following the
instructions in SYNTAX and
Sinclair's schematic.

On my second system I wired
the new keyboard to an externally
accessable plug. I tapped off
necessary connections on the ZX80
(8K/16K) and mounted its plug at
the top of the case where my modu-
lator used to be (I removed the
modulator after I ran direct video
out). This way I have portability
or big keyboard features depending
on where I'm computing.

Key caps on both keyboards
were made from photocopied origin-
als. Elmers glue holds them down.
Spread a little extra on the tops
to protect them from wear (it dries
clear).

The keyboard also has a myriad
of other helpful hardware such as a
speaker with volume control, four
switches (I used one for power and
one for video select) and a number
of small lights. Allin all, a
very worthwhile investment.

Russ Gagnon, Oscoda, MI

I don't know of anyone in the US
selling the MicroAce board now.
For info about Meshna's keyboard
(#SPL-19), contact Doug Meshna, PO
Box 62, E. Lynn, MA, 01904, 617/
595-2275.--AZ

Jan.82 p.9 "More Hardware
Hints" contains a number of useful
hints, but you might find Cramolin
better for cleaning and preserving
metal-metal contacts. Old Colony
Sound Labs, Audio Amateur, Box 243,

Peterborough, NH 03458, sells both
Cramolin cleaner and preservative
for $9.95 (there are other
sources). I would clean and
protect the board edge contact of
any ZX80/1 sent to me with return
postage and $2.00.

Ron Miller, 3488 Douglas Drive,
Murraysville, PA, 15668

USERS' GROUPS

We have received notice of these
users's groups since last month.

To check for a group in your area,
call or drop us a note with a SASE.
If you belong to or want to start a
ZX80/81 users' group, let us know
and we'll pass it on.--AZ

Los Angeles, CA: George Kuby,
213/550-5035 after noon or P.O. Box
34545, Los Angeles, CA, 90034.

San Francisco/San Jose, CA: Paul

Perrault, Stanford Telecommunica-
tions Inc., 1195 Bordeaux Dr..,
Sunnyvale, CA 94086, 408/734-5300
x267.

Seattle/Tacoma/Everett, WA: Dan
Gallery, 1619 E. John St., #414,
Seattle, WA 98112, 206/325-8186.

Denver, CO: Cap Hamilton, 767 S.
Gaylord St., Denver, CO 80209,
733-6857.

Fort Wayne, IN: Sinclair Midwest
Users' Group, Robert Carroll, P.O.
Box 13042, Fort Wayne, IN 46866.

Lynchburg, VA: Lynchburg Microcom-
puters Users Group, Lane Lester,
804/237-5961 Div. of Natural
Science.

Central Pennsylvania: Bill
Russell, RD 1 Box 539, Centre Hall,
PA 16828, 814/364-1325.

New York, NY: ZX Users' Group of
New York, Box 560 Wall St., New
York, NY 10005.

COMPUTER CHESS — JUST $24.95

ZX81 CHESS: a challenging game written
in superfast machine code for the
SINCLAIR ZX81 (req. 16K rampak)

Improve your game: Choose from six levels of play, novice to expert. The
ZX81 gives a graphic display of board position and keeps separate records of
your moves and the computer’s. Make any legal move, including Castling
and Enpassant; illegal moves not accepted.

Refine your strategy: Set up board to any configuration, even change sides
midgame. Elect ‘‘Random Mode”’ — computer won’t always make the same
move in identical situations. Another bonus: a chess clock that records and
displays time per move.

To purchase your ZX81 CHESS package, send check or money order

@) MINDWARE CO.

70 Boston Post Road
Wayland, MA 01778

(postpaid, but add sales tax in Mass.) to:

HARDWARE REVIEW

Product: 4K/8K ROM Switch
From: Marex Electronics, 2805
Abbeyville Rd., Valley
City, OH 44280
Price: basic kit, $24.95,

assembled, $30.95; full-
feature kit, $34.95,
assembled, $49.95

The Marex ROM switch lets you
use both your 4K and 8K ROMs on a
ZX80 (a 4K ROM won't work on a
ZX81). The basic kit comes with a
3" square PC board with plated-
through holes, sockets and compon-
ents, plus spacers and screws to
put the case back together with the
PC board inside. An extra $10 gets
you the full-feature kit, which
also gives cassette-load automatic
gain control, a keyboard beeper and
a reset-upon-ROM-switch so you
don't have to pull the plug every
time you switch ROMs. For kit
assembly, you need wire cutters, a

16

soldering iron, small screwdriver
and pliers, drill and pen knife.

I put together the basic kit.
It came with step-by-step direc-
tions, parts list, schematic and
board layout drawing showing where
everything goes. All the parts
arrived, including about a foot of
solder. Although not a hardware
person, I had no trouble soldering
the components to the board and
plugging it into the computer.

But I did have trouble getting
it to work. First, the directions,
though very clear and simple, don't
tell you how to avoid zapping your
ROMs with static electricity. Not
a big problem here at SYNTAX, where
ROMs abound, but if you have only
2, it could be tough. Then we
found a short between 2 ROM pins on
the PC board. Rex Rickly of Marex
tells us he caught this fault in
one other board, and no one else
has gotten one. It seems that some
plated holes are too large, so the
traces sometimes run too close,
causing shorts.

Rex sent an assembled, tested
board, and it works quite nicely.
One of our ZX80s, which always
resets slowly (several seconds with
1K RAM), would not work with the
ROM switch board. But this machine
only works marginally as it is.

If your luck runs better than
mine and you get a good board, keep
these things in mind: ground your-
self when handling ROMs. When
removing a ROM from the ZX80, touch
the modulator (silver box in the
rear). When you plug the ROMs into
the new board, push them all the
way in (till the pins pop into
place) to make good contact. Yet
be careful not to bend the pins--
they might snap. Three capacitors
on the ZX80 board will get in the
way--bend these down carefully
until the ROM socket pins can plug
into the socket on the ZX80 board.
With these precautions and a gocd
PC board, you'll be able to use
either ROM without removing one
each time, risking broken pins.--AZ

THE FLAGS REGISTER

(This is part 3 of 12 short pieces
on machine code programming on the
ZX80/1--AZ)

The Flags register, F, is the
other half of the Accumulator pair,
AF. The Accumulator (or A regis-
ter) is where the results of
operations (like add and subtract)
are stored. The Flags register
tells you something about the value
in the A register. AF is just like
the other register pairs HL, BC,
DE, etc., except that the AF pair
changes with each manipulation; all
of the others change only when
specifically instructed to do so.

Instead of values for each bit
position, the Flags register holds
information for testing. Each bit
stands for a different condition
and can be either 0 or 1 (0=flag
not set, l=flag set). Each bit
represents the information:

FLAGS (F)

S Z- = Ho~ P/O N.C
(bit)0 0000 0 0 0
ACCUMULATOR (A)

128 64 32 16 8 42> 7
(bt#). 90. Oh OO 2G OO 26

Bit 7--S sign (0 if +, 1 if -)

6--Z zero (0 if result of oper-
ation WAS NOT 0, 1 if result
WAS 0)

5--not used

4--H half carry (used intern-
ally, not testable)

3--not used

2--P/O parity/overflow (parity
is testable)

1--N add or subtract (used
internally, not testable)

O--C carry (l is a carry from
the Accumulator)

Most nonprofessional machine
code programmers need thoroughly
understand only the Z flag. The
others can be studied when neces-
sary. For instance, if you have an

address in REM for data (<128; + or
- value), you can load A with that
value, test bit 7 (the Z flag) to
see if it is positive or negative,
then continue depending on what is
in the Z bit.

Here's what happens: when bit
7 is tested, the Z flag will show 0
if the bit is 1 (negative value) or
1 if the bit is 0 (positive value).
It sounds confusing, but just
remember 0 in the Z flag means
negative; 1 means positive. If the
next instruction is JR Z (jump
relative to Z), then the computer
will jump if Z=1 (similar to
IFf...THEN GOTO in BASIC). If Z=0,
the computer just goes to the next
instruction.

The Z80 offers thousands of
possible bit-test/test-and-branch
combinations...try a few.

Next: LOADING REGISTERS WITH DATA
Jon Bobst,
35225

Zeta Software, PO Box
SC, 29608-3522

Greenville,

BANI-l ECH

Software of the Month Club

Get the most from your ZX81 with 16K, use it to
its full potential, while building an impressive in-
ventory of software. Receive twelve listed programs—
one a month. Programs like Income Tax Recording,
Auto Maintenance, Household Expenses, Price of
Gold Forecasting, Diet Planning, Scrooge’s Christmas
Gift and Card List and many, many more for the
incredibly low price of just $19.95 per year. Save
your valuable time and get down to basics!
Make checks payable to BANI-TECH

P.O. Box 1568

Princeton, N.J. 08540

O My check for $19.95 is enclosed.
Please charge my O Mastercard O Visa

Account Number — Exp

Signature

Name
Address

City

SYNCHRO-SETTE

FOR THE ZX-80 & ZX-81
8K ROM 1K- 16K
GAMES-EDUCATIONAL-BUSINESS
GRAPHICS-TUTORIAL-ETC.

SOFTWARE REVIEW

Programs: Video-Plan,
Computacalc
Price: V-P £9.95 deluxe,
£7.95 standard
cc $39.95 US
ROM/RAM: 8K/16K, ZX81 only
From: V-P--Video Software Ltd.

Stone Lane, Kinver, Stourbridge,
West ‘''dlands, UK DY7 6EQ
CC--Mindware Co., 70 Boston-:-Post
Rd., Wayland, MA 01778 (written by
Silicon Tricks, London)

Electronic spread sheets (like
Visi-Calc) let you analyze or model
business and financial problems
quickly and easily. You can try
changes, make corrections, and play
with alternatives. Any task using
rows/columns of numbers you can
carry out with these two programs.

Computacale and Video-Plan run
on ZX8l1s with 16K RAM. Neither
runs on upgraded ZX80s. Both are
written in BASIC, run slowly, can

18

be LISTed, work with ZX printers,
have mostly OK input error trapping
and recovery, left-justify entries
(decimal points do not line up),
and let you force recomputation.

Neither program lets you move
rows or columns automatically, nor
can you insert rows or columns. As
a user, I miss these functions. As
a rotten typist, I also miss the
ability to edit complex formulas.

Each program emphasizes a
different approach to analysis--CC
is cell-oriented, V-P is column-
oriented.

Documentation for each program
is poor. The notion persists among
software suppliers that one manual
can serve to sell, instruct, exem-
plify, explain, and catalog. Once
you learn to use the program, you
will find looking through the
examples just to find a command
annoying. Of the two, V-P did the
better job.

CC's manual fits in the
cassette case--4 1/2 columns of
type set 13 lines to the inch.
get an example that demonstrates
most commands, a list of options to
respond to the major prompt, and
two hints to modify the program.

V-P uses larger type and
provides a 19-page booklet that
covers similar topics. Three pages
describe suggested applications,
and three are devoted to titles and
contents. Each menu option is
fully described by telling the
consequences of each permissible
response. Chapter 5 on functions
lacks clarity and does not explain
which columns may have subtotals.

In most cases the effect of
erroneous entries is explained.
Both programs can behave badly
without warning the user, though CC
exhibited fewer of these problems.
Any long tape can load with a few
errors which may cause the program
to crash after a while. That's a
needless annoyance--run the
Syntactic Sum of these programs
when you first get them and at
every load thereafter.

You

V-P exhibited defects so
serious that I must rate it

unacceptable until they are cleared KOPAK GIVES

to eucnd) el tie: algal eos sar YOU THE POWER!
totals can be arithmetically
incorrect; and you can confuse the

KOPAK’STM Touch-A-Matic gives you KOPAKT is now offering The Source*
the power to type more accurately and ‘America’s Information Utility’, The

program so that the s prea d sheet much faster. No wires, no soldering, Source* gives you the power to access
7 simple to install. Our unique vinyl over- a wide array of services including:
calculates . ub totals at int ervals lay guides your fingers to the correct e Barter e Shopping ¢ Business Infor-
other than those you asked it to. keys. Touch typing now possible with mation ¢ Career Network @ Electronic
1 1 your Sinclair* or MicroAce*! Mail ¢ Medical Advice ¢ UPI News
All of these pieaiaea without warning. $9.95 Service and much more. A modem is
CC can give the usual least- required to use The Source*.
signicant-digit error between row The KOPAKTM Sinclair* female Con- sence SA
. nector gives you the power to use the
and co lumn totals » res (hte ing from Z-80 bus. Edgecard connectors specif- More POWER on the way! KOPAK’STM
round-off error. ically made for Sinclair* computers. Coming Creations:
* © 46 Pins, 23/23 « All pins are gold The KOPAKTM RS-232 Interface

* Both pro grams 7 prov1 de huge plated ¢ polarizing pin for correct The KOPAKTM Bus
grids, much to their detriment. alignment everytime! Available with The KOPAMATICTM Keyboard

- . * Solder-Tail, Wire-Rap and PCBoard. The KOPAKTM Printer
Neither gives you any direct con- $14.95 KOPAKTM Memory Products
trol over grid size, and both The KOPAKT™ Disc
calculate the whole grid every ‘KOPAK has the POWER to deliver!”
time. V-P took about 10 minutes to

© 1982 KOPAK Creations Inc.
reto tal the sheet after changes “ie KOPAK Creations Inc. TM Trademark of KUPAK Creations Inc.
most annoying. CC is much faster Dept. SX Sinclair* is a trademark of Sinclair*
. 448 West 55th Street Research LTD.

when you use sma Le por tions of the New York, NY 10019 MicroAce* is a trademark of MicroAce*

sheet since it only calculates (212) 757-8698
formulas you put in, whereas V-P
always does all row functions and
column totals--nice, but slow.

V-P only allows functions 8K FLASHING PROMPTS SUBROUTINE
between columns, but displays the
function below the column at all To avoid screen flicker, I
times. In CC, you define cell came up with this subroutine (at
relationships freely, but you'll 200 in this example). The example
never see them again unless you program gives 6 flashing prompts.
write them down. The function To change the number of flashes,
labels just serially number the change 6 in line 145. For differ-
formulas you put in. ent periods between flashes, change

V-P handles titles separately 3 in line 215. Run in SLOW mode.
from data, so they don't scroll off
the screen, but V-P doesn't move Rois Harder, N. Van, B.C., Canada
the row titles and data together as |............. dre well af no Canes
it does the column labels. CC
treats the labels as data, and

48@ PRINT AT 21,6;"“10 TO 143"

scrolls them off screen on large 2@5 PRINT AT 21,0; “INPUT”
grids. Neither program provides a oc BeSue Soe
title lock, nor does either let you 120 PRINT AT 21.08; “Re
adjust the row title size 125 GOSUB 2a a -
independent of the data block. ace Basue Bon te sii a

Despite the shortcomings, I am 240 LET P=Pii
delighted to see programs of this wee cota see Saha oe
type becoming available for the ISS INPUT AS :
ZX81. Computacale is a usable Sec oe oe aa :
program and both are recommended 2i@ IF T=S THEN RETURN =

for programmers who want to see how

SYNTACTIC SUM: 19457, 68K
to do these functions in BASIC.--KO ° ce ceeds

19:

INCREDIBLE!

2X80/1 Users

RKE16 Expanded Memory - 16K
RKL-32 Expanded Memory - 32K
RKL-J1" Single Joystick System
RKL-J2* Dual Joystick System
30-Day Money Back Guarantee
Fully Assembled and Tested
* Includes Demonstration Program

SUPER PACKAGES!

79.95
149.95
69.95
89.95

Super RKL-A

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Super RKL- B
32K Memory plus
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RKL Systems

POBox 515
Leominster MA 01453

219.95

Incluge 4.95/shipping + handling
Check or money order

CURING 16K RAM RANDOM DUMPING

My 16K RAM pack tended to dump
its memory if my ZX81 was moved,
wiggled, or tapped, or if the RAM
pack was squeezed. Sometimes it
dumped for no apparent reason. I
suspected the problem was caused by
dirty contacts at the edge connec-
tor, but cleaning the contacts had
no effect. The cause was mechani-
cal instability in the RAM pack
itself. The problem took only five
minutes to fix, and now my ZX81l
with 16K attached can withstand any
amount of wiggling, shaking or
thumping without a memory dump.
This procedure worked for me:

e Open the RAM pack case by remov-
ing the 4 screws and pulling the
halves apart gently. Inside are 2
boards hinged together at the top
by a ribbon cable, book-fashion.

e Inside the front and rear halves
of the case you'll find large tan-
colored cardboard insulators. With
a: pair of ‘scissors; trim the

BOOK REVIEW
Title: Machine Language Program-
ming Made Simple for Your
Sinclair ZX80 and ZxX81

By: Melbourne House Publishers
Price: $19.95, 160 pgs, paperback

I wanted to review this book
because I'm the person it was
written for. The ZX80 and ZX81
have been my only computers. I
taught myself BASIC and can now do
most of the things I want to with
it. I felt that machine language
(ML) would be a good addition to
speed up some programs and improve
display. The idea of ML "made
simple'' appealed to me.

This quality spiral-bound
volume starts on a very elementary
level, explaining how the computer
counts and stores numbers. It goes
through the various registers for
both the ZX80 and ZX81. You learn
to manipulate the registers and
keep track of them. |

Each ML command is explained
with exercises as learning aids.

At the end two fine indexes list
the Z80 commands both by number and
alphabetically by mnemonic code.
All instructions are in hexidecimal

notches in the insulators so they
just clear the screw posts.

e On a lower corner of the front
board (the one with the blue plug
attached) you will note 2 grounding
springs that are designed to make
contact with the metallized coating
of the case when it is assembled.
Inspect this area of the board to
see if the pins running from the
blue plug project far enough above
the rear of the board to make
contact with the grounding springs
when they are flexed. If this
appears possible, nip off the
projecting pin ends as close as
possible to the surface of the
board and cover them with a piece
of vinyl electrical tape.

e On the boards in my unit, only 2
of the electrolytic capacitor cans

20

numbers, not decimal. Most
articles I've seen are in decimals.
Being uninitiated to ML, my
main problem was: what do you do
with it? I felt like I learned all
the skills of woodworking but not
to build anything. A program com-
bining BASIC and ML is included at
the end, but I found it hard to
follow and felt it lacked suffici-
ent explanation to make it useful.
Don't order this book for
quick ML routines to plug into your
programs. Instead, you'll find a
book that seems to give a good
background in ML to help you under-
stand and build on further informa-
tion found in other articles.
Michael Roberts, Des Moines, IA
This book doesn't offer immediate
applications, but it's the best
explanation of ML for ML beginners
I've seen. Its friendly style is
painless reading and simple analo-
gies help make this language clear.
This introduction is a must before
moving to books like Zak's Program-
ming the Z80. From from Gladstone
Electronics, 901 Fuhrmann Blvd.,
Buffalo, NY, 14203, or 1736 Avenue
Rd., Toronto, Ontario, M5M 3Y7.--AZ

had vinyl electrical tape on top of
the cans to prevent shorting to the
opposing board when the boards were
folded together. Place vinyl tape
on top of ALL the cans, and as an
extra precaution stick a strip of
tape on the bottom surface of the
opposing board.

e Reassemble the RAM pack, making
sure that the lower grounding
spring on the front board makes
contact with the metallized coating
on the inside of the of rear half
of the case. If necessary, bend it
gently to insure that it makes _
proper contact. The side grounding
spring will be pinched between the
two halves of the case when it is
properly assembled.

Burt Haberman, Tuscon, AZ

21

CLASSIFIED ADS

Reach 19,000 ZX80 and ZX81 users
for $2.75/line, 4-line min. Send
ad, typed 35 char/line, with check/
credit card no. by 15th of month
for next month's issue to SYNTAX,
RD 2 Box 457, Harvard, MA 01451.

Coming soon - ZX81 Monopoly

16K RAM-up to 6 players-imported
from the UK. British board version
family game. Savage PO Box 2681
Kirkland, Washington. 98033

7 1K ZX81 GAMES ON CASSETTE--$10.00
Mastermind, Slot Machine, Craps,
Sub Rescue, White Hot Number, and
more. NEW ENGLAND SOFTWARE, Box 691,
Hyannis, MA 02601. (Also for ZX80)

Get loaded every time on ZX-80/81
with LED monitor. Plans $1; Kit
$6+ $1 ship. Play basketball (2
sep. games avail.) in 4K/1K &
8K/2K, $1.50 per list. Send money

+ SASE to: R&H Enterprises, 1408 N.
Newton,

4th Ave. E., IA 50208

Available from SYNTAX...

For computing beginners —

Crash Course in Microcomputerts.............. $17.50
Covers hardware, machine language and
applications. Reviewed in SYNTAX, Oct. 1981.
Add $1.50 shipping.

ZX80 Pocket Book..............ssssssccssssssssseseseess $14.95
Includes ZX81 supplement. Covers Sinclair
BASIC, data and program listings.

Add $1.50 postage.
For advanced hardware/software users —

Zilog’s Z80-Z80A CPU

Technical Manal.............ccccsssssssssccsesssreeceves $7.50
Zilog’s Assembly Language
Programming Manuall................sscccssssceoses $15.00

Add 5% for shipping.

4K ROM Listing with Sinclair’s Original
Designer’s Annotations................ssccseseeeees $40.00
Original listing plus utility programs.

SYNTAX back issues available, $4 each.
Call or write for our group subscription discounts.

SYNTAX ¢e RD2Box457 ¢ Harvard, MA 01451
617 / 456-3661

SIMULATED LEARNING for your ZX81/0!
Think of animal; computer tries to

guess it.Computer learns from mis-—
takes for next time. List, instr.,

cassette (good stuff! 8/16K)$12.50.
Foreign add US$3. SMUG PROJECT, PO

Box 13042, Fort Wayne, IN 46866

FOR SALE: ZX-81,16K RAM,Radio Shack
Minnisette recorder,cables,manuals
$225.00. Also ZX-80,8K ROM,cables,
manuals, $100.00. Send cashiers ck
or M.0O.:V.R.Haupin, Hydrostorage,
Confederate Dr,Franklin TN 37064.

OFFICIAL SHOW GUIDE for 2nd ZX
Microfair held Jan. 30 1982--46
pages, listing all major suppliers
of ZX81 software and peripherals--
$2.49 each.

ANIMATED GRAPHICS SUBROUTINE--very
clear, well written primer on how
to do graphics on the Zx8l.
Includes demo program, listings and
subroutines--$2.95 each. Send
check or m.o. to Mindware Co., 70
Boston Post Rd., Wayland, MA 01778

WANTED: ZX-80, 8K ROM, 1K RAM and
all paraphernalia that came with
the machine upon original purchase,
especially programmers manual.
State sales offer in writing,
including telephone number, and
mail to: Michael Wido

2922 Kendale, Apt.

Dallas, TX 75220

142

BANTA SOFTWARE now offers Football,
Murder in the RAM,Casino,& our ori-
ginal-Super Monzxer-taped for $3.95
each.Also,we will write programs to
your specs for reasonable $$. BANTA
SOFTWARE,RD #7,Bethlehem, PA 18015

TAX RETURN HELPER: A set of ZX81
(16K RAM) programs let you easily
enter/examine/modify the forms and
immediately compute the results of
any change. You can also save the
data for future use. Form 1040 and
Sched A,B,C $10 (tax deductible),
Same plus Sched D,E $14. KSOFT, 845
Wellner, Naperville, IL 60540.

22

Coming Soon - CP Productions. We
will have everything from Adventure
Games to Chess, Cooking,to SAT
Vocabulary and Space Games to
Checking Account Balancing. Send
for a free list of coming programs.
CP Productions, P.O. Box 247, Big
Horn, Wyoming, 82833.

ZX81/16K QUICK CUBE--guaranteed to
solve any’ Rubik's Cube (TM) or
triple your money back. Cube is
set up by entering 54 color faces
of cube. Cube is then solved via
150-200 rotations. Pause control
available at each cube rotation
display. Very interesting program.
Also available for TRS-80 (TM)
I/III, 16K, Level II BASIC. Send
$19.95 for either program, plus
$1.50 postage and handling, to
Alpha Queue Systems, Dept. D, P.O.
Box 20885, Dallas, Texas 75220.
Texas residents add 5% ($1) state
sales tax. Remit checks or money
orders only please. TM--registered
trademarks of Ideal Toy Company and
Radio Shack.

"Coin Collection''Mass data storage.
Menu: add/delete, check inventory,
change cost/value,total cost/value,
search,self running/saving & more.
(Listable)8K ROM/16K RAM.TapetInst.
$9.95+$1.05P/H.Programs custom/made
Send a SASE with descript.,example,
and title for free est. M.C.Hoffman
542 Clinton Rd, Paramus, N.J. 07652

16K GAMES FOR THE ZX81/ZX80 8K ROM

ZX8 TREK - 5 levels of difficulty
with 20 battle command options.

CRIBBAGE - the computer challenges
you at the game of Cribbage.

TANK BATTLE - find the computer's
tank before it locates yours.

Cassette + manual - $14.95 ea. game

A.Nisbet, 6 Moffat Court, Rexdale,

Ontario, Canada, M9V 4El1.

#6116 2K x 8 150 NS Static Ram Chip
Available for delivery @ $19.00
plus $1.00 for shipping. Send
check or MO to: Support Systems
One, PO Box 1794, Phila., PA 19105

MAGIC SQUARE. World's Most Magic!!!
16x16 More Magic thn BEN FRANKLIN's
Probe with ZX. $2.00 EZRA GROUP II
Box 5222 San Diego,California 92105

LATEST SOFTWARE FOR ZX81 - Games,
practical, math and more! Lowest
Prices Anywhere! Also, Loading
Filter plus other accessories.
Write for FREE catalog to:

GREAT LAKES SOFTWARE, 201 Burlington
Road, Valparaiso, IN 46383

OUR POLICY ON CONTRIBUTED MATERIAL

SYNTAX ZX80 invites you to express opinions related to the ZX80 and the
newsletter. We will print, as space allows, letters discussing items of general interest.
Of course, we reserve the right to edit letters to a suitable length and to refuse
publication of any material.

We welcome program listings for all levels of expertise. Programs can be for
any fun or useful purpose. We will test run each one before publishing it, but we
will not debug programs; please send only workable listings.

In return for your listing, we will pay you a token fee of $2.00 per program we
use. This payment gives us the nonexclusive right to use that program in any form,
world-wide. This means you can still use it, sell it, or give it away, and so can we.

We will consider submissions of news and hardware or software reviews. Please
keep articles short (350-400 words). Again, we reserve the right to edit accepted
articles to a suitable length. We will pay 7 cents per 6 characters, including spaces
and punctuation, for accepted articles.

When you send in programs for possible publication in SYNTAX, please
include the following information:

¢ How to operate the program, including what to input if it does not contain

prompts.

© Whether you can run the program over again and how.

© How to exit the program.

° The Syntactic Sum (using the Syntactic Sum program in the February, 1981,

issue).

© Whether it fits in IK or 2K RAM (or 16K when available).

© Whether it uses the 4K or 8K ROM.

We pay for this explanatory text at the same rate as for articles in addition to
payment for the program itself.

If you want us to return your original program listing or article, please include
a self-addressed, stamped envelope. Otherwise, we cannot return submitted material.

SYNTAX ZX80 is published

monthly by a wholly-owned
subsidiary of The Harvard Group.

Syntax ZX80, Inc.

RD 2, Box 457, Harvard, MA 01451.
Telephone 617/456-3661.

account number

**KKLOOKING FOR SOMETHING DIFFERENT
*to run on your Z81? How about some
*thing that lets you investigate
*your past life,...or,find out just
*what turns on that special person.
*How? 'Astrology'--based on ancient
*knowledge about the harmonic quan-
*tazation of energy -Astrology does
*work! And now,you can write a pro-
*fessional personal horoscope. Check
*mate compatability,analyse person-
*alities.Not only locates 9 planets
*moon,node,houses,but prints out an
*interpretive analysis,-making it a
*sreat party game.Tape $16.Visa/MC.
*914-2555521.LS,POB 935,New Paltz,
*NY.12561.Astrology trainer incll6K

LAND THE SPACE SHUTTLE. Your TV
screen becomes the instrument panel
and windshield of the spacecraft.
The runway appears before you,
giving the effect of a flight simu-
lator. Game has several endings,
each dependent upon your skill.
LAND/AIR BATTLE. Destroy the enemy
(the computer) before it destroys
you. Fly the aircraft through flak
dropping bombs on target. For ZX81
and slow screen Microace 8K Rom.16K
Ram. Get both games on one tape for
$6.95. Funware 7119 Santa Fe Ave.
Dallas, Tx. 75223

YES! Please send me 12 issues of SYNTAX for $29.

My check for $29 is enclosed.
Make checks payable to:
SYNTAX ZX80, INC.

(] Please charge my [1] MasterCard
C] Diner’s Club (J American Express
[] VISA ( Carte Blanche account

|
|
i]
|
t
1
|
12 issues, $29. Single issue, $4. 1) ADs date bank number (MC only)
| Signature
Publisher: Kirtland H. Olson Dar Title
Editor: Ann L. Zevnik I
woe
Printed by Joseph E. Marhefka, Jr. Oretizaion
Clinton Offset Printers ! Address
Clinton, MA 01510 | City State Zip
© Syntax ZX80, Inc., 1981. All ; Day Phone_( eae Evening Phone ( )
|
|

rights reserved. Photecopying
prohibited. ISSN 0273-2696

I own a LJ Sinclair ZX80 UC Sinclair ZX81

617-456-3661

ZX815

Telephone orders call

BUFFERED EXPANSION BUSS for ZX80/81

For memory mapped peripherals.

Unlimited applications. Perfect for

experimenting w/computer hardware.

BARE BOARD AVAILABLE NOW

*fully buffered, w/decoders to open
8K of I/O space. Needs 8 chips.

*4 connector positions to fit .156"
c/c 44 pins popular circuit cards.

*2 connector positions to fit .1"
c/c. *Room for wire wrap.

*all components readily available.

*fingers for 16K memory pak.

*complete documentation plus free
plan for T/0 port:

*plated thru holes..legend..solder
mask..gold plated fingers

*provision for 3A voltage regulator

BARE BOARD (w/one connector

GO CRE COMPUDEL) cause ewes! od S30:
Shipping and handling........ oot
Calif.residents add $1.95 S.Tax

Allow 4-6 weeks delivery.

To order: specify for ZX80 or

ZX81 and send check to:

COMPUTER CONTINUUM, 301 16th Ave.

San Francisco, CA 94118

Product price/availability subject
to change without notice.

(ZX80 w/8K ROM will require minor

circuit modification).

Complete kit available next month.

TELE
HARVARD
GROUP

Bolton Road, Harvard, Mass. 01451

24

EZRA GROUP II
EZRA GROUP II
The ZX80/81's are making a name
with LOW prices...
WE CHALLENGE THE SOFTWARE COMPANIES
TO LOWER THEIR PRICES!
for ZX81/ZX80/8k ROM
1K and 16K RAM versions
BLGTNYE NMS: s-5 sn xa) Ree ead! Snort
Graphics Billboard os ees wiw Rader 3 b.00
SPINNER T.M. (like Rubik's) 16K..2.00
Skew-a-Sketch(like Etch)
Improved Pause(ZX81)...........
Linear “Proer ami ne hc vee ee Ask.
Self Addressed Stamped Envelope
Gets YOU Our goodies catalog
ALL ORDERS AND CATALOG REQUESTS GET
FREE Galactic Messages PROGRAM.
EZRA GROUP II
EZRA GROUP II
P.O. Box 5222 San Diego,
(714) 584-8291

California
92105

TEXT EDITOR: (8KROM/16KRAM) Enter and
edit any text or graphic, list/docmt
$10.w/all updates $20. D.O'connell

1219 W.Russell,San Antonio TX 78201

PUT THAT ZX80/81 TO WORK with SORT.
This great collating tool can count
and file 1000s of items in over 29
categories with just 1K! $3 gets

you list & notes to learn/build on.
Tom Woods Box 64 Jefferson,NH 03583

U.S. Postage
PAID
Harvard, MA
Permit No. 8
01451

First Class